So, I'll try and be concise, but I tend toward verbosity, so...
Which programming language would be beneficial to learn to efficiently create host PC-based user interfaces (graphical and nongraphical) that communicate via COM ports to embedded hardware? I'm mostly talking about rather simple, straightforward window-based (not necessarily MS Windows-based) UIs with buttons, sliders, fields, etc. that communicates via PC ports to appliance hardware. Commands sent by UI software, data sent back by embedded system, outputs plotted graphically, etc.
I have zero experience with this, so it is pretty much blank slate. I have some novice experience with Python and C. C proficiency will be increasing over time. I'm looking for something that would be quick to employ once I got my basic proficiency. Bonus would be OS-agnostic during runtime, but not a strict requirement.
I sometimes see other people with amazing hardware projects that involve PC control (and display/user interface) and wonder how they go about making the PC-side of things. I'm sure there's more than one way to go about this, so I'm not really looking for "the one true way" more just some brainstorming on ideas.
For example, I understand how Java uses a runtime environment and compiles to bytecode and how this lends itself toward platform compatibility. This seems interesting to me, but I wouldn't know enough to know how important this even is.